A blend of one or more crosslinked polymers or copolymers prepared from an olefinically unsaturated polymerizable carboxylic or anhydride monomer and at least one high molecular weight essentially linear polymer prepared from an olefinically unsaturated polymerizable carboxylic acid monomer. The blend is neutralized to typically a low pH, and generally contains a noncovalent, e.g. ionic, crosslinking agent, and a cure rate modifier. The hydrogel blend is capable of containing a large amount of water, has good tack, good adhesion, and can be utilized as an application vehicle having a backing thereon as well as containing various substances such as personal care compounds, pharmaceuticals, active ingredients, and the like. Conversely, the hydrogel blend can be dried and subsequently wetted without substantial loss of properties.

1. Field of the Invention
The present invention relates to articles created using blends of polymers and other ingredients, and to a process for preparing the same. The articles serve as a hydrogel for applying various substances to a substrate. The substance can be a personal care compound, a biologically active compound, an active ingredient, an absorptive material, etc. The substrates can be living organisms, or inanimate objects. The hydrogels after being formed, can be dried to facilitate ease of handling. The dried hydrogels can be rewet as by an open wound, blood, etc. without substantial loss of properties.
2. Background Art
The earliest cataplasms were probably called poultices. A poultice is a medicated mass (often clay, herbal component, and a carrier such as water) spread on cloth and applied to the skin, often for sores or other lesions. Later, various gels and viscosity modifiers were added to cataplasms. Typically and preferably, a cataplasm has direct contact with skin or the substrate to be treated. As prepared commercially in a multiple cataplasm package, a cataplasm often has a backing on one side, which provides physical strength and a durable exposed surface during use on the substrate, and a release layer on the other side, which is removed before application to the substrate.
Transdermal delivery systems have been developed for various pharmaceutical applications. They generally transfer a medicine through the skin rather than to the skin. The active ingredients in commercial transdermal delivery systems are usually limited to a single chemical compound or a family of compounds. These systems are typically more expensive than oral medication and comprise an impermeable backing layer, a reservoir, a metering layer, and an adhesive layer. The system is usually protected by a release layer.
Hydrogels containing various substances or compounds such as personal care compounds, pharmaceuticals, etc., are described. The hydrogel contains significant amounts of water therein and is a blend of a crosslinked polymer and a high molecular weight essentially linear polymer. Noncovalent crosslinks, such as ionic crosslinks in the presence of cure rate modifiers, permit the hydrogel to be formed into a suitable end product before being cured.
The hydrogel compositions of the present invention can be dehydrated as in the form of a film, sheet, membrane, layer, etc., through conventional methods either in-situ or after being applied to a backing. Upon re-wetting, the film, sheet, membrane, layer, etc., reverts to a gel with physical characteristics substantially similar to the pre-dried hydrogel composition. Advantages of the dried hydrogel composition include direct application to a wound, mucous areas of the body, and the like. Other advantages include easier packaging, stabilization, less costly shipping, and customer convenience.
From a compositional aspect, the hydrogel is a blend of at least two polymers one of which is a crosslinked polymer derived from one or more olefinically unsaturated polymerizable carboxylic monomers and optionally one or more comonomers. The other polymer is a high molecular weight substantially linear polymer derived from one or more olefinically unsaturated polymerizable carboxylic acid monomers. The hydrogel also contains a neutralizing agent; desirably a noncovalent crosslinking agent; and a cure rate modifier; and is generally located on a backing with a release compound or liner covering the hydrogel. The hydrogel is typically applied to a substrate such as human skin and contains therein a substance such as a personal care compound, a pharmaceutical, an active ingredient, or the like; The hydrogel is typically located on a substrate.
In some embodiments, the hydrogel removes a compound from the substrate by binding an absorptive substance to the substrate. That is, the hydrogel and its active ingredient act as absorbents of an impurity or irritants. An example of this would be the removal of undesired oil or other components from the skin. The hydrogel offers a new way to deliver or remove some compounds (those not before applied with cataplasms) to/from various substrates with improved performance attributes.
The hydrogel comprises any natural or synthetic polymer that is highly swollen by water. In the cataplasm application the hydrogel and its backing desirably remain a coherent mass, i.e. it doesn""t fracture during application, removal, or use and can be discarded as a single unit of waste. It is generally desired that none of the hydrogel, other than the delivered substance, remain on the substrate after use. The backing can be any material convenient to the particular application. It is generally only present for ease of handling and integrity purposes, although it can facilitate application and solvent retention. Wovens, nonwovens, and films such as plastic can be used as backings. Natural or synthetic products can also be used. The release liner can be any suitable material known to the art or to the literature and generally is a plastic which optionally contains a release agent thereon such as a silicone.
Desirably the hydrogel is crosslinked or otherwise linked together as an integral material (e.g. a polymer and/or a noncontinuous hydrogel can be connected together via interentanglement of the chains, crystalline crosslinks, ionic crosslinks, hydrogen bonds, etc). For the purposes of this specification, integral will mean some connection, either temporary or permanent, that allows the hydrogel to function as a solid at typical storage and use temperatures of the particular substance. Function will imply that the hydrogel does not unduly flow, fracture, or fragment during use, but understandably does not imply tremendous physical integrity, which is not generally required. The preferred polymers forming the hydrogel will be gel-like particles that have the capacity to increase their volume by swelling in water by a factor from about 10 to about 1000 or 10,000. Preferably, they swell from about 10, 20, 30, or 40 times to about 500 or 1000 times their original volume.
Polyurethanes may also be used in the hydrogel. These may be thermoplastic or elastomeric polyurethanes. They may be hydrophobic, hydrophilic or amphiphilic depending on the active ingredients or other additives to be incorporated into the hydrogel. Polyurethanes and their precursors are well known to the art. It is preferred that the polyurethanes only be an additive to the hydrogel and that they be appropriately functionalized or processed to be uniformly dispersed in the hydrogel.
According to the present invention, an olefinically unsaturated polymerizable carboxylic monomer is utilized. Such monomers are described in detail and set forth in U.S. Pat. No. 5,468,797, as well as prior U.S. Pat. Nos. 5,373,044, and 5,288,814 thereof, which are hereby fully incorporated by reference with regard to all aspects thereof. As set forth in the ""797 patent, the monomer contains at least one activated Cxe2x95x90C group as well as a carboxyl or anhyride group. Such polymers can be homopolymers of an unsaturated, polymerizable carboxylic monomer containing from 3 to 34 carbon atoms, and preferably from 3 to 6 carbon atoms such as an acrylic acid, methacrylic acid, maleic acid, itaconic acid, maleic anhydride, and the like. The carboxyl containing polymers, before crosslinking, have molecular weights greater than about 500 to as high as several million, usually greater than about 10,000 to 900,000 or more.
Copolymers of the polymerizable carboxylic monomers can be made utilizing monomers having a total of from 3 to about 40 and desirably from 3 to about 34 carbon atoms such as acrylate esters, acrylamides, olefins, vinyl esters, vinyl ethers, vinyl amides, amines or styrenics. The amount of repeat units derived from such comonomers is generally from about 0.001 to about 30 percent and desirably from about 0.01 to about 20 percent by weight of the copolymer.
Typical materials are those described in U.S. Pat. No. 2,798,053. Copolymers, for example, include copolymers of acrylic acid with small amounts of polyalkenyl polyether cross-linkers that are gel-like polymers, which, especially in the form of their salts, absorb large quantities of water or solvents with subsequent substantial increase in volume. Other useful carboxyl containing polymers are described in U.S. Pat. No. 3,940,351, directed to polymers of unsaturated carboxylic acid and at least one alkyl acrylic or methacrylic ester where the alkyl group contains 10 to 30 carbon atoms, and U.S. Pat. Nos. 5,034,486; 5,034,487; and 5,034,488; which are directed to maleic anhydride copolymers with vinyl ethers. Other types of such copolymers are described in U.S. Pat. No. 4,062,817 wherein the polymers described in U.S. Pat. No. 3,940,351 contain additionally another alkyl acrylic or methacrylic ester and the alkyl groups contain 1 to 8 carbon atoms. Carboxylic polymers and copolymers such as those of acrylic acid and methacrylic acid also may be crosslinked with polyfunctional materials as divinyl benzene, unsaturated diesters and the like, as is disclosed in U.S. Pat. Nos. 2,340,110; 2,340,111; and 2,533,835. The disclosures of all of these U.S. patents are hereby incorporated herein by reference.
The carboxylic monomers are the olefinically-unsaturated carboxylic acids containing at least one activated carbon-to-carbon olefinic double bond, and at least one carboxyl group; that is, an acid or function readily converted to an acid containing an olefinic double bond which readily functions in polymerization because of its presence in the monomer molecule, either in the alpha or beta position with respect to a carboxyl group, xe2x80x94Cxe2x95x90Cxe2x80x94COOH; or as part of a terminal methylene grouping, CH2=C less than . Olefinically-unsaturated acids of this class include such materials as the acrylic acids typified by acrylic acid itself, methacrylic acid, alpha-cyano acrylic acid, beta methylacrylic acid (crotonic acid), alpha-phenyl acrylic acid, beta-acrytoxy propionic acid, cinnamic acid, p-chloro cinnamic acid, 5-phenyl-2,4pentadienoic acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, aconitic acid, maleic acid, fumaric acid, and tricarboxy ethylene. As used herein, the term xe2x80x9ccarboxylic acidxe2x80x9d includes the polycarboxylic acids and those acid anhydrides, such as maleic anhydride, wherein the anhydride group is formed by the elimination of one molecule of water from two carboxyl groups located on the same carboxylic acid molecule. Maleic anhydride and other acid anhydrides useful herein have the general structure
wherein R and Rxe2x80x2 are selected from the group consisting of hydrogen, halogen and cyanogen (xe2x80x94Cxe2x89xa1N) groups and alkyl, aryl, alkaryl, aralkyl, and cycloalkyl groups such as methyl, ethyl, propyl, octyl, decyl, phenyl, tolyl, xylyl, benzyl, cyclohexyl, and the like.
The preferred carboxylic monomers are the monoolefinic acrylic acids having the general structure
wherein R2 is a substituent of hydrogen, halogen, and the cyanogen (xe2x80x94Cxe2x89xa1N) groups, monovalent alkyl radicals, monovalent aryl radicals, monovalent aralkyl radicals, monovalent alkaryl radicals, and monovalent cycloaliphatic radicals. Of this class, acrylic and methacrylic acid are most preferred. Other useful carboxylic monomers are maleic acid and its anhydride.
The above noted polymers can be crosslinked with any polyene, e.g. decadiene or trivinyl cyclohexane; acrylamides, such as methylene bis acrylamide; polyfunctional acrylates, such as trimethylol propane triacrylate; or polyfunctional vinylidene monomer containing at least 2 terminal CH2 less than  groups, including for example, butadiene, isoprene, divnyl benzene, divinyl naphthalene, allyl acrylates and the like. Particularly useful cross-linking monomers for use in preparing the copolymers are polyalkenyl polyethers having more than one alkenyl ether grouping per molecule. The most useful possess alkenyl groups in which an olefinic double bond is present attached to a terminal methylene grouping, CH2=C less than . They are made by the etherification of a polyhydric alcohol containing at least 2 carbon atoms and at least 2 hydroxyl groups. It is preferred to utilize polyethers containing an average of two or more alkenyl ether groupings per molecule. Other crosslinking monomers include for example, diallyl esters, dimethallyl ethers, allyl or methallyl acrylates and acrylamides, tetraallyl tin, tetravinyl silane, polyalkenyl methanes, diacrylates, and dimethacrylates, divinyl compounds such as divinyl benzene, polyallyl phosphate, diallyloxy compounds and phosphite esters and the like. Also, polyallyl esters of poly(methacrylic acid) can be utilized. Typical agents are allyl pentaerythritol, allyl sucrose, trimethylolpropane triacrylate, 1,6-hexanediol diacrylate, trimethylolpropane diallyl ether, pentaerythritol triacrylate, tetramethylene dimethacrylate, ethylene diacrylate, ethylene dimethacrylate, triethylene glycol dimethacrylate, and the like. When the crosslinking agent is present, the polymeric mixtures usually contain up to about 5% or more by weight of crosslinking monomer based on the total of carboxylic acid monomer, plus other monomers, if present, and more preferably from about 0.01 to 3.0 weight percent by weight.
Preferred crosslinking agents include allyl pentaerythritol, trimethylolpropane diallylether, and allyl sucrose.
In addition to the above described polymers and copolymers, an interpolymer of the same, can also be utilized. Such interpolymers are made by preparation of the above polymers or copolymers in the presence of a steric stabilizer surfactant. The steric stabilizer surfactant has at least one hydrophilic moiety and at least one hydrophobic moiety in a linear block or a random comb configuration, or mixtures thereof. The interpolymer can be mixed with a wetting additive such as a low surface tension surfactant, a glycol, a polyhydric alcohol, or mixtures thereof.
A detailed description of the preparation of the interpolymers, the steric stabilizer surfactants, the wetting additive, and the like is described in detail in U.S. Pat. No. 5,468,797 and accordingly is fully incorporated by reference. When the steric stabilizer is a linear block copolymer steric stabilizer, it is defined by the following formula:
Cwxe2x80x94(Bxe2x80x94Axe2x80x94BYxe2x80x94)xe2x80x94xDz,
where
A is a hydrophilic moiety, having a solubility in water at 25xc2x0 C. of 1% or greater, a molecular weight of from about 200 to about 50,000, and selected to be covalently bonded to the B blocks;
B is a hydrophobic moiety, having a molecular weight of from about 300 to about 60,000, a solubility of less than 1% in water at 25xc2x0 C., capable of being covalently bonded to the A blocks;
C and D are terminating groups which can be A or B; can be the same or different groups, and will depend upon the manufacturing process, since they are present to control the polymer length, to add other functionality;
w is 0 or 1;
x is an integer of 1 or more;
y is 0 or 1; and
z is 0 or 1.
Examples of hydrophilic groups are polyethylene oxide, poly(1,3-dioxolane), copolymers of polyethylene oxide or poly(1,3-dioxolane), poly(2-methyl-2-oxazoline polyglycidyl trimethyl ammonium chloride, polymethylene oxide, and the like, with polyethylene oxide being preferred. Examples of hydrophobic groups are polyesters, such as those derived from 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxycaproic acid, 10-hydroxydecanoic acid, 12-hydroxydodecanoic acid, 16-hydroxyhexadecanoic acid, 2-hydroxyisobutyric acid, 2-(4-hydroxyphenoxy) propionic acid, 4hydroxyphenylpyruvic acid, 12-hydroxystearic acid, 2-hydroxyvaleric acid, polylactones such as caprolactone or butyrolactone, polylactams such as those derived from caprolactam, polyurethanes, or polyisobutylene, where the hydrophobe should provide a steric barrier of greater than 50 Angstroms, preferably greater than 75 Angstroms, with greater than 100 Angstroms being also preferred, and the like, with polyhydroxy fatty acids, such as poly(12-hydroxystearic acid) being preferred. The steric barrier is the length of the hydrophobe in its fully extended condition. Such steric stabilizers are commercially available under the brand name Hypermer(copyright) from Imperial Chemicals Industries, Inc.
Steric stabilizer molecules comprise both hydrophilic and hydrophobic units. Hydrophobic polymer units or hydrophobic blocks may be prepared by a number of well known methods. These methods include condensation reactions of hydroxy acids, condensation of polyols (preferably diols) with polycarboxylic acids (preferably diacids). Other useful methods include polymerization of lactones and lactams, and the reactions of polyols with polyisocyanates Polyisobutylenes can be prepared by acidic condensation of isobutene. Hydrophobic blocks or polymer units can be reacted with hydrophilic units by such reactions as are known to those skilled in the art. These reactions include condensation reactions and coupling reactions, for example. Subsequent to the steric stabilizer preparation, the stabilizers may be further reacted with modifying agents to enhance their utility. U.S. Pat. No. 4,203,877 to Alan S. Baker teaches making such steric stabilizers, and the entire disclosure thereof is incorporated herein by reference.
When the steric stabilizer is a random copolymeric comb steric stabilizer, it is defined by the following formula:
R1xe2x80x94(Z)mxe2x80x94(Q)nxe2x80x94R2,
where
R1 and R2 are terminating groups and may be the same or different and will be different from Z and Q.
Z is a hydrophobic moiety having a solubility of less than 1% in water at 25xc2x0 C.,
Q is a hydrophilic moiety, having a solubility of more than 1% in water at 25xc2x0 C.,
m and n are integers of 1 or more, and are selected such that the molecular weight of the polymer is from about 100 to about 250,000.
Examples of the hydrophobic monomer unit or moiety are dimethyl siloxane, diphenyl siloxane, methylphenyl siloxane, alkyl acrylate, alkyl methacrylate, and the like, with dimethyl siloxane being preferred.
Examples of the hydrophilic monomer unit or moiety are methyl-3-polyethoxypropyl siloxane-xcexa9-phosphate or sulfate, and the alkali metal or ammonium salts derived therefrom; units derived from polyethoxy (meth)acrylate containing from 1 to 40 moles of ethylene oxide; acrylic acid; acrylamide; methacrylic acid, maleic anhydride; dimethyl amino ethyl (meth)acrylate; or its reaction product with methyl chloride or dimethyl sulfate; dimethyl amino propyl(meth)acrylamide and its reaction product with methyl chloride or dimethyl sulfate, and the like, with methyl-3-polyethoxypropyl siloxane-xcexa9-phosphate being preferred.
Examples of terminating agents are monohalo silanes, mercaptans, haloalkanes, alkyl aromatics, alcohols, and the like, which will produce terminating groups such as trialkyl silyl, alkyl, aryl alkyl, alcoholate, and the like, with preferred terminating groups being trimethyl silyl.
The wetting additive is preferably a low surface tension surfactant (or wetting agent) and can be a fluorine containing, silicone containing or hydrocarbon surfactant, as long as it has an ability to reduce the surface tension of water (which is 72 dynes per centimeter at 25xc2x0 C.), preferably to less than 40 dynes/cm at 25xc2x0 C., with less than 30 dynes/cm being further preferred. By the term hydrocarbon surfactant we mean any surfactant which contains carbon, hydrogen, and oxygen and does not contain fluorine or silicon atoms. The amount of low surface tension surfactant will usually be less than 10% by weight based upon the weight of the acrylic acid interpolymer (10 phr), although 0.001 phr to 5.0 phr is preferred. The exact amount will depend upon the surfactant which is selected and its ability to reduce the surface tension of water. Those surfactants which can be used at the least dosage, such as a fluorine containing surfactant are preferred. Further, it was unexpectedly discovered that some of the surfactants are quite effective at very low dosages, such that the surfactant has no or little effect on the properties of the interpolymer in its use as a thickener, emulsifier, or thickening aid. Although not fully understood, it is believed that some of the surfactants when used in greater doses will result in increased wetting times because the additional surfactant will provide an additional coating on the polymer particles and slow the wetting process.
Table I shows a list of low surface tension surfactants which can be used in accordance with the present invention. The surface tension values represent the ability of a 1% by weight dosage of these surfactant to reduce the surface tension of water at 25xc2x0 C. As can be appreciated, this list is considered representative and other low surface tension surfactants could be employed.
The surfactant employed can be anionic, cationic, or nonionic with nonionic surfactants being preferred. When the surfactants is added prepolymerization, the cationic and anionic nature of the surfactant can play a part in or influence the polymerization, while the nonionic surfactants remain relatively inactive.
The wetting additive can be added to the monomers in polymerizing the polycarboxylic acid interpolymer or after polymerization, or in the case of the low surface tension surfactants, it also can be added to the water into which the interpolymer is to be dispersed. It is preferred that the wetting additive be admixed after or post-polymerization. It is theorized that, when the surfactant is added during polymerization, it remains with the polymer as an admixture, but a portion of the surfactant is trapped in the interstices of the interpolymer, so the same amount added pre-polymerization will not be as effective as that amount added post-polymerization of the interpolymer. Further, there is nothing critical in the method of addition. For example, the surfactant can be added as a liquid to the interpolymer while it is still in the polymerization, solvent and before drying or it can be sprayed on the dry polymer powder which can then be subject to further drying.
The glycol and polyhydric alcohol are most preferredly admixed after polymerization, and provide little or no benefit when added to water into which the interpolymer is to be dispersed. It is reasoned that the presence of the alcohol functionality will interfere or interact with the acid functionality of the acid polymer being formed. When added to the polymer post-polymerization, it is possible to control the conditions, such as excessive heat when drying, which could lead to interference or interaction.
The polyhydric alcohols are organic hygroscopic compositions, usually alcohols, which facilitate the wetting of the interpolymer particles in water. For the purpose of this disclosure, we mean the term xe2x80x9cpolyhydric alcoholsxe2x80x9d is to include all hygroscopic alcohol compositions including glycols, such as polyethylene glycol. The use of either a low surface tension surfactant or a polyhydric alcohol benefits the wetting of the polymer particles by aiding the wetting of the water by lowering the surface tension of the water and allowing it to penetrate the polymer particle or by drawing the particle to the water (or the water to the particle) via the hygroscopic mechanisms. As will be seen either benefits the wetting of the polymer without detriment to the use of the polymer as, e.g., a thickener.
The preferred polyhydric alcohols are glycerine (or glycerol). The preferred glycol is low molecular weight polyethylene glycol. Other polyhydric alcohols (or polyols) or glycols can be employed.
Examples of preferred linear block copolymeric steric stabilizers and random copolymeric comb steric stabilizers include fluorinated alkyl polyoxyethylene ethanols such as Fluorad FC-170C, fluorinated alkyl alkoxylate such as Fluorad FC-171, and ammonium perfluoralkyl sulfonate such as Fluorad FC-120, all made by 3M.
The relative proportions of the steric stabilizer based upon the total weight of the olefinically unsaturated polymerizable carboxylic monomers and optional comonomers is generally from about 0.001 to about 20 percent, desirably from about 0.01 to about 10 percent, and preferably to about 0.2 to about 6.0 percent by weight.
The above crosslinked polymers, copolymers and interpolymers made from one or more olefinically unsaturated polymerizable carboxylic monomers are commercially available as Carbopol(copyright)980 NF from BFGoodrich. Generally, other such crosslinked polymers, copolymers, etc., are available as various CARBOPOL(copyright)D polymers from BFGoodrich, as various PEMULEN(copyright) polymers from BFGoodrich, as various NOVEON(copyright) polymers from BFGoodrich, as various HIVIS WAKO(copyright)D polymers from Wako Junyaku Kogyo, and as various SYNTHALEN(copyright) polymers from 3 V Sigma.
It has been found that hydrogels capable of absorbing large amounts of water having unexpectedly low initial viscosities, and yet good tack and adhesion, as well as strong cohesion forces, which result in a rigid gel, are formed by blending the above crosslinked polymers, derived from olefinically unsaturated polymerizable carboxylic or anhydride monomers, with a high molecular weight substantially linear polymer derived from an olefinically unsaturated polymerizable carboxylic acid monomer. Such olefinic unsaturated acid monomers generally contain a carboxyl group and a total of from 3 to about 20 or 30 carbon atoms and preferably from 3 to about 7 carbon atoms. Specific examples include acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, citraconic acid, aconitic acid, fumaric acid, and the like. Preferred acids include acrylic and methacrylic, with acrylic acid being highly preferred. By the term xe2x80x9csubstantially linearxe2x80x9d polymers which are derived from the olefinically unsaturated polymerizable carboxylic acids, it is meant that the polymer generally has 5 or less, desirably 3 or 2 or less, and preferably 1 or less side chains for every 100 repeat units of the polymer. Such polymers have a weight average molecular weight of generally from about 50,000 to about 2,000,000, desirably from about 200,000 to 1,000,000, and preferably from about 400,000 to about 600,000. Examples of suitable long chain high molecular weight polycarboxylic acids include CARBOPOL(copyright) 907, GOODRITE(copyright) K-702 and K-709 from BFGoodrich.
The polymeric blend is generally formed by dispersing a crosslinked polymer derived from olefinically unsaturated polymerizable carboxylic monomers into water. The amount of the polymer is generally from about 5 parts to about 30 parts by weight and desirably from about 10 parts to about 15 parts by weight for every 100 parts by weight of water. Similarly, the high molecular weight, linear polymer is dissolved in water in an amount of from about 5 to about 40 parts by weight and desirably from about 10 to about 20 parts by weight for every 100 parts by weight of water. The high molecular weight, linear polymer and the crosslinked polymer are then blended together. Optionally, additional water or other solvent such as alcohols, polyols, or polyalkoxides can be added. Such additional water or solvent is dependent upon the desired final qualities and physical constraints of individual formulations.
It has been found that the degree of neutralization of the hydrogel polymer blend has a direct impact on the ability of the blend to be noncovalently crosslinked; e.g., ionicly crosslinked or crosslinked by hydrogen bonding. Accordingly, the crosslinked polymer or copolymer and high molecular weight linear polyacid is partially neutralized from an initial pH of from about 2.5 to about 3.5 to a pH of from about 3.5 to about 14, or about 10, or about 6.0, and desirably from about 4.2 to about 5.2. Neutralization can be carried out with any convenient neutralizing agent or compound such as ammonium hydroxide, sodium hydroxide, other alkali hydroxides, borates, phosphates, pyrophosphates or polyphosphates; AMP-95 (2-Amino-2-Methyl-1-Propanol) a product of Angus Chemical, cocamine, oleamine, diisopropanolamine, diisopropylamine, dodecylamine, Peg-15 cocoamine, morpholine, tetrakis(hydroxypropyl)ethylenediamine, triamylamine, triethanolamine, triethylamine, or tromethamine (2-Amino 2-Hydroxymethyl-1,3-propanediol). Preferred neutralizing agents include NaOH, tetrakis(hydroxypropyl)ethylenediamine, triethanolamine.
A viable non-covalent crosslinking system for the blend of a crosslinked polymer derived from olefinically unsaturated polymerizable carboxylic monomers and the high molecular weight linear polymer includes ionic crosslinkers such as polyvalent metal ions such as aluminum and zinc. The plus-3 oxidation state for aluminum is preferred and the plus-2 oxidation state for zinc is preferred. Desired compounds generally include halogen salts such as AlCl3, ZnCl2, MgCl2, CaCl2, BCl3, BF3, and the like. Sufficient amounts of the polyvalent metals are required to achieve crosslinking. Below a critical amount, the resulting hydrogel is too fluid. Above a critical amount, the metal ions are absorbed into the carboxyl forming an overly rigid, non-adhesive hydrogel The use of chemical crosslinks or the use of polymers already including chemical crosslinks in the form of microparticles or microgels can minimize the amount of ionic crosslinkers that are needed. This is desirable as the ionic crosslinkers may undesirably interact with many of the substances such as an active ingredient, decreasing the efficiency of delivery and sometimes preventing delivery. Reduction of the amount of ionic crosslinkers typically reduces any deleterious effect of the ionic crosslinkers. The amount of such ionic crosslinkers is dependent on the desired physical characteristics of the hydrogel and interactions with its various substances.
Other non-covalent crosslinking compounds include various crystallite crosslinked polymers such as polyvinyl alcohol, and the like.
Still other types of non-covalent crosslinking compounds include various hydrogen bonded compounds such as various complexes of polyacrylic acid with at least the following compounds: polyfunctional Lewis bases such as polyvinyl alcohol, polyvinyl pyrrollidone, polyethylene imine, polyethylene oxide, polypropylene oxide, glycosylated proteins, macromolecular polyols, polyacrylamide, and polysaccharides.
In order to prevent overly quick curing of the polymer blend and the formation of a rubber-like hydrogel, various cure rate modifiers are utilized such as monoalcohols, diols, and/or polyols such as glycerol. Examples of monoalcohols include methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and t-butanol and monoethers of ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, and mixed ethylene oxide/propylene oxide glycols. Examples of diols include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, ethoxy diglycol and hexylene glycol. Other suitable curing rate modifier agents include sugar solutions (xylitol, sorbitol), PEG (POE, polyoxyethylene, polyethylene glycol), PPG (polypropylene glycol), PEG/PPG (copolymers or blockpolymers), and the like. The amount of the alcohol utilized is generally from about 1 to about 80, desirably from about 10 to about 50, and preferably from about 20 to about 30 parts by weight for every part by weight of the ionic crosslinking agent.
The utilization of a cure rate modifier is to allow the hydrogel to be suitably shaped before cure occurs. For example, the hydrogel can be applied as a film to a backing such as nonwoven material, etc., as described herein above.
The hydrogel blends of the present invention are generally only partially swollen with respect to the full amount of water they can absorb. Such deficient amounts of water generally include from about 2 to about 10 and desirably from about 3 to about 5 times their original linear dimension. Otherwise, too much water results in too weak of a hydrogel, such that the adhesive force is stronger or greater than the cohesive force of the gel.
The hydrogel of the present invention can be utilized in various forms. One desired form is a so-called patch wherein the hydrogel containing the curing agent and the cure rate modifier, etc., is spread on a suitable backing. A release liner is then applied to the top of the hydrogel. The hydrogel is then allowed to cure. Another suitable form is a hydrogel in the form of a sheet or layer which contains a release layer on either side thereof or on both sides thereof. The hydrogel containing a substance therein be it a personal care compound, a pharmaceutical compound, an active ingredient, a biological active compound, an absorptive material, etc., can be wrapped in a suitable container such as an impervious plastic wrap, foil pouch, etc., and stored until needed. Then it can be applied to a desired substrate as noted herein below.
The applied substance can be any material known, purported, or thought to have beneficial effect on the chosen substrate such as the substances listed in the preceding paragraph. While water-soluble active ingredients are most easily incorporated, the use of nonwater carriers, emulsifiers, dispersed organic (hydrocarbon) phases, etc. can allow the delivery of nonpolar compounds (e.g. hydrocarbon materials such as aliphatic and aromatic compounds).
One class of substances are the therapeutic aids which include, but are not limited to, moisturizers (or things that help the substrate (skin) retain water); oils (or things that help the skin retain oil); antimicrobial agents; antibacterial agents; fungicide; anti-inflammatory/analgesic agents (e.g. things that reduce irritation): softening agents; toughening agents; agents that enhance elasticity of the substrate (e.g. skin); agents that enhance abrasion resistance of the substrate (e.g. skin, fabric, apparel), that provide some slipperiness to skin or fabric, or prevent pilling of fabric by other mechanisms; agents that otherwise change the texture of the substrate; agents that promote growth or cell reproduction; agents that retard growth or cell reproduction; stimulants for the cells or nerves; antihistamines; local anesthetics; etc.
The substance may remove unwanted components from the substrata such as removing oil, greases, irritants, nail polish, etc.; removing blemishes, defects, unusual texture, scars, growths (e.g. warts); removing hair; etc.
The hydrogel may apply an active ingredient with one or more of the following advantageous properties: sustained delivery, consistency in, dosage, enhanced delivery, dosage control, efficiency, and bioavailability for: wound healing, burn healing, scar reducing, etc.; skin or keratin color changes (lightening, darkening, coloring), applying decorative images, highlighting; enhancing penetration of another active ingredient or medicine through the skin or other substrate; altering the fragrance or aroma of the substrate; reducing or enhancing fat, e.g. cellulite reduction; applying a hormone, steroid, or pheromone-, etc.
The active ingredient of the hydrogel may be of any polarity from low to high including fragrances, coloring, pigments, ointments, etc. Where desired, water solubility may be enhanced by the addition of other carriers, additives, etc. In many embodiments, a mixture of two or more active ingredients which act independently or in conjunction with each other will be used. The active ingredient can be any of the following: a moisturizer; an anti-aging agent (removing aging effect or repairing aging effects); an astringent; an acid (e.g. glycolic, citric, and vitamins); a skin stimulator (e.g. menthol, camphor, and cayenne pepper extract); a firming agent; a slimming agent; a radical scavenger; solubilizers; an antihistamine (e.g. diphenhydramine or chlorpheniramine maleate); methyl salicylate; glycol salicylate; an aromatherapeutic; a humectant; an emollient; a phytochemical (natural extract such as herbal and botanical e/.g. bamboo, tea tree oil, etc.); an antioxidant; a skin whitening agent (e.g. hydroquinone, peroxide, and kojic acid); a self tanning agent or agent for adding skin colorant (e.g. dihydroxy acetone); a skin protecting agent (e.g. moisturizers, waxes, sunblocks (organic or inorganic)); a spot remover (substrate may be people, clothing, animals, plants, hard surface, or fabric); keratin; retinol; vitamins; vitamin complexes; precursors of active ingredients such as precursors of retinol; salicylic acid and derivatives of salicylic acid; peptide; oligomeric and polymeric peptide; an enzyme; a coenzyme; proteins and their precursors; amino acid (e.g. dimers, cyclic and aliphatic amino acid); glycosamineoglycans; saccharides; derivatives of saccharides; polysaccharides, oligomeric saccharides; cyclic oligomeric saccharides; carbohydrates; fatty acid triglycerides, essential fatty acids; lipids; lecithin; phospholipids; conditioning agents; milk derivatives, carotenes; cyclodextrins; tocopherols; phytosterols; cationic agents; oil (natural such as animal and vegetable, synthetic including primrose oil, jojoba oil, mineral oil, castor oil, palm oil, coconut oil, corn oil, silicones, and derivatized forms thereof); gelatins, natural starch, modified starches, cellulosics and chemically modified cellulosics, sodium alginate, acacia, corn starch, casein, natural gums, and/or modified natural gums; waxes (natural such as plant and synthetic); quaternized compounds; silicone and/or silicone derivatives; protein hydrolyzates or derivatized proteins; chitin; denatured chitin; chitosan; marine derived compounds or marine origin materials (e.g. anything from the sea including things such as kelp, coral, seaweed, marine moisturizing factor, algae, sea plants, phytoplankton, kelp, and their extracts); hydrolyzed animal and/or vegetable protein; astringent (e.g. zinc oxide, tannic acid, alum, aluminum sulfate, vitamin, dl-xcex1-tocopherol); a wetting agent; a water repellent; an antimicrobial; a deodorant; a fungicide; a fruit acid; nut extracts/oils; a fragrance; flower acids; ceramides; a flavinoid; biologically derived materials (biotechnology); sodium hyaluronate; hyaluronic acid; etc.
It is also anticipated that the active ingredients can be added to the hydrogel after being blended with, contained within, and/or bound to another medium (liquid/solid or other). Examples include encapsulated ingredients, nanospheres, actives in zeolites, actives in oil, actives in liposomes, actives in glycospheres, etc.
The above substance added to the hydrogel be it a personal care compound, a pharmaceutical, an active ingredient, or the like, is generally added over a broad range of amounts depending upon the particular type of substance and the desired end result. The substance can be added to the blend of polymers prior to neutralization, or after neutralization but prior to ionic crosslinking or hydrogen bonding crosslinking. Alternatively, the substance can be added after the addition of the crosslinking agents but prior to the same curing. The crosslinking time will vary depending upon the amount of the various cure rate modifiers utilized and also upon the type of polymers utilized. As a rough rule of thumb, the desired cure time is approximately several hours to several days.
Substrates for application of the hydrogel compound include the skin, hair, and fingernails. The hair and fingernails can be grouped in the class of keratinous substrates. While personal use by humans is a preferred embodiment, uses on animals, plants, etc is not excluded. Hair substrates can be temporarily or permanently changed in color (including decorative images), texture (including adding or removing curls in hair), and for prevention of microbial, bacterial, and fungal activity on the substrate surface.
Substrates also include apparel, fabrics, hard surfaces, and vehicles including automobiles. For these substrates the improvements include but are not limited to sustained delivery (e.g. volatile components trapped in the hydrogel do not evaporate as quickly as when applied directly to the substrate and are available to the substrate over the entire treatment period), consistency in dosage, enhanced delivery, controlled dosage amount, efficiency, etc. A preferred embodiment for these substrates is those applications or active ingredients, which are adversely affected by atmospheric oxygen. The exposure of the substrate surface to atmospheric oxygen is restricted during the time the cataplasm is in place and this allows more effective use of oxygen sensitive compounds. Depending on the particular substrate and cataplasms for these substrates, the stability at various storage and use temperatures can vary widely.
The physical integrity of the hydrogel is desirably such that fracture and/or fragmentation of the hydrogel does not occur during storage and use. If the hydrogel is adhesive or has an adhesive layer attached thereto to better secure its relative location on the substrate during delivery or removal of the active ingredient(s), then the hydrogel desirably has a cohesive strength in excess of the adhesion value to the substrate.
The hydrogel, in addition to the substance, can contain various conventional additives in any desired amount. Such additives include clay, herb and herbal extracts, chemical compounds and materials which absorb undesirable components from skin or other substrates, adsorption enhancers, desorption enhancers, absorption enhancers, humectants (e.g. glycerin, propylene glycol, sorbitol), water miscible or immiscible organic solvents (or other active carriers or active reservoirs), adhesive and/or a polymer that imparts adhesivity to the hydrogel (e.g. polyvinyl alcohol)xe2x80x94may be important to adhere cataplasm to backing or adhere cataplasm to substratexe2x80x94, gel support media or polymer to interconnect hydrogel particles, modulus modifier, tensile strength modifier, elongation to break modifierxe2x80x94these conform the hydrogel and cataplasm physical properties to the application requirementsxe2x80x94, gelation rate regulator (e.g. EDTA, citric acid, lactic acid, tartaric acid, and polyacrylic acid, also called chelating agents), additives to reduce negative interaction by hydrogel to substrate (irritation, inflammation or corrosion)xe2x80x94may be as simple as pH adjuster, oil, wax, etcxe2x80x94, etc.
A preferred form of application of the hydrogel is in the form of a patch wherein the hydrogel is located on a backing and the hydrogel optionally has a release liner thereon. The backing can be made of any suitable natural or synthetic fiber or fabric, and can be woven or non-woven. Examples of fibers or natural fabrics include cotton, wool and the like. Examples of synthetic fibers or fabrics include polyester such as polyethyleneterephthalate, polyethylene, polypropylene, nylon, acetate and the like. The backing can also be in the form of an impermeable or permeable foam made from natural materials or from synthetic materials such as polyolefin, polyester, polyurethane, and the like. Thickness of the backing can vary widely as from 1, 3 or 5 to about 10, 20, 30, 40, and even 50 mils. The release liner can be a plastic such as a polyolefin, for example polyethylene or polypropylene, or it can be polyvinylchloride, nylon, and the like. Optionally, it can contain a release liner thereon such as a thin layer of silicone. The patch can be applied to a substrate such as human skin simply by removing the release liner and applying the hydrogel, containing the backing thereon, thereto.
In a further embodiment of the present invention, the hydrogel compositions are dried or dehydrated, permitting easier packaging, less costly shipping and customer convenience. Subsequently, the dried or dehydrated composition can be rewetted and hence regain substantially all of the original aqueous composition""s adhesive and viscoelastic properties. Preferably the dehydrated hydrogel is advantageous applied to various portions of a person such as an open wound, blood, mucus, fluid, or a moist area, etc.
After the hydrogel is formed from the above noted compounds, active ingredients, additives, etc., hereby fully incorporated by reference, the aqueous hydrogel compositions can advantageously be dried, dehydrated or made substantially non-aqueous. The aqueous hydrogel compositions can be dried through any conventional methods known to the art and literature. Examples of suitable drying methods and/or equipment include but are not limited to drying ovens, drying tunnels, vacuum driers, high temperature air baths, freeze drying, extruded with venting, and combinations thereof. The aqueous hydrogel compositions can even be dried under ambient conditions. Generally, any temperatures can be utilized to dry the hydrogel composition so long as the polymers therein are not degraded. Drying temperatures generally range from 0xc2x0 C. to about 120xc2x0 C., desirably from ambient, i.e. room temperature (eg. 20xc2x0 C.) to about 80xc2x0 C. or 100xc2x0 C., and preferably from ambient temperature to about 30xc2x0 C. The water content range after drying generally ranges from less than or equal to about 95 or 75 percent to about 0 or 0.1 percent, desirably less than or equal to about 50 percent, 30 percent, 20 percent, 15 percent, or 10 percent, and preferably less than about 5 percent of the total water weight originally present in said hydrogel composition before drying.
The aqueous compositions can be dried to form various products such as a sheet, film, membrane, layer, etc. The thickness ranges for the dried products are generally from about 0.01 or 0.1 to about 100, 200 or greater mils, desirably from about 2 mils to about 100 mils and preferably C3 from about 5 mils to about 50 mils. The dried hydrogel products of the present invention can be applied or adhered to various backings, as described hereinabove and hereby fully incorporated by reference, so as to form a layered product such as a laminate, a patch, etc.
Alternatively, the aqueous hydrogel compositions of the present invention can be first spread or applied in desired amounts to a receptive backing, as set forth hereinabove and fully incorporated by reference, forming a layered product such as a laminate, a patch, etc., and then subsequently dried. Utilizing this method, the hydrogel dries and sticks or otherwise bonds with the backing and no adhesive is necessary.
The dried hydrogel which optionally has a backing, can be rewet prior to, in the course of, or in-situ after application to a desired substrate. Upon rewetting , the hydrogel layer reverts to a gel layer with physical characteristics substantially similar to the pre-dried gel layer. More specifically, the adhesion integrity is maintained, and viscosity returns to the range present before drying. Desired substrates are the same as those listed above and are hereby fully incorporated by reference.
However, preferred substrates include persons and especially portions thereof such as a body, legs, arms, etc., and include open wounds, mucus membrane areas, and the like wherein moisture, blood or other liquid or fluids can serve to rewet or to rehydrate the dried hydrogel (with or without water) and thus return the same to a gel layer. Thus, the hydrogel can be directly applied to a wound, cut, broken skin, lesion, mucus, area, etc.
Other benefits of the dried hydrogel include less costly shipping due to lighter weight because of dehydration of the water content. The dried hydrogel compositions are easier to package as no precautions need to be taken to keep the hydrogel from drying out or losing moisture. End users also enjoy the convenience of a dry film product that only needs to be moistened for use.


The present invention is directed to turf grass seed mixtures for a low maintenance lawns and uses therof. The lawn established from the specific seed varieties blended in certain proportions as described in the disclosure has a slow growth rate and deep roots and grows well in many regions across North America and elsewhere in the world. Because the lawn requires little watering or fertilizer and is hardy and naturally insect-tolerant, it is safe and environmentally friendly.

A staggering amount of chemicals including pesticides, herbicides and fertilizers are used every year on lawns, causing run-off and unnecessary health risks. Between 50% and 80% of lawn care chemicals run off lawns with the rain and into storm drains, ending up in the watershed or local ponds, lakes, streams and rivers. This causes algal blooms and feeds the invasive weeds out of control. In addition, many local communities use expensive herbicides in an effort to eliminate the invasive weeds in the ponds. Low levels of the fertilizer, pesticides and the herbicide may end up in local drinking water. Use of pesticides and fertilizer in urban and suburban communities contributes significantly to contamination of our drinking water and other surface water supplies. This also increases health risks to children, pets and the elderly and increases school department budgets from learning and behavioral disorders caused by the lawn care chemicals. Such use of chemicals applied to lawns adversely affects the entire community in many ways, increasing the risk to a wide range of public health problems, as well as incurring high costs of clean-up and dealing with invasive weeds.
Lawn care chemicals and pesticides get carried indoors into homes on shoes, pets and air currents. Once inside, pesticides linger in carpets, dust, on toys, and in the air we breathe. These chemicals normally break down outside over time with sunlight. However, away from sunlight and water, lawn chemicals and pesticides persist for many months, resulting in longer exposure to these chemicals indoors. According to health experts at the Massachusetts Department of Environmental Protection, prolonged exposure to the pesticides, herbicides and fertilizers in lawn care chemicals is responsible for an alarming increase in the risk of learning and behavioral disorders in children, and an increased risk for asthma, Parkinson's disease, cancer and a number of other ailments. The increased health risks are much higher for children, the elderly and our pets. According to Dr. Margo Roman, a veterinary expert, "50 years ago, only 5% of dogs got cancer. Today, over 46% of dogs get cancer and there is evidence suggesting this is caused by the widespread use of lawn care fertilizers, herbicides and pesticides." In response to these concerns, according to a report from the Organic Consumers Association "a new era" in pesticide use has begun in many cities around the globe, including all of Canada, New York City, San Francisco and many European cities, with the banning of many domestic products containing chemicals considered toxic to humans and the environment, including certain lawn-care chemicals.
Some estimates indicate that 30% of our county's precious potable water is consumed for lawn care uses. Lawn irrigation, particularly in-ground watering systems, increase summer water use to levels 3 to 5 times higher than winter water use. Use of nitrogen-rich chemical fertilizers and fast-growing, high-maintenance, shallow rooted grasses exacerbates the problem. Water shortages from your neighbors lawn care leads to increased water prices for everyone, water bans, and enforced conservation. Many of the non-native lawn seeds from Europe or Kentucky, with very shallow roots, are naturally adapted to environments that are wetter than ours. In New England, and most of North America, these foreign, shallow root, high maintenance grasses leads to an unnatural pattern of frequent watering and frequent mowing, particularly if chemical fertilizer is used.
Watering lawns with water that is filtered for human consumption and pumped to our homes wastes huge amounts of energy. Much of this lawn irrigation water evaporates and never returns to the underground water table. Producing commercial fertilizers from petroleum is energy intensive, and costs are rising as oil prices rise. Running a typical lawn mower for an hour is 11 times more polluting than running a mid size car full of people and luggage for an hour. So the energy intensive fertilizer, water from the town and lawn mower pollution in a standard lawn greatly increases your home and family carbon foot print. The May 2008 issue of "Health" Magazine had a story about the 12 most toxic things around your home environment, noting that a chemically-maintained lawn is the single most toxic thing inside or outside a home environment.

Low-maintenance lawn seed mixtures and use thereof


Antireflective compositions characterized by the presence of an SiO-containing polymer having pendant chromophore moieties are useful antireflective coating/hardmask compositions in lithographic processes. These compositions provide outstanding optical, mechanical and etch selectivity properties while being applicable using spin-on application techniques. The compositions are especially useful in lithographic processes used to configure underlying material layers on a substrate, especially metal or semiconductor layers.

In the microelectronics industry as well as in other industries involving construction of microscopic structures (e.g. micromachines, magnetoresistive heads, etc.), there is a continued desire to reduce the size of structural features. In the microelectronics industry, the desire is to reduce the size of microelectronic devices and/or to provide greater amount of circuitry for a given chip size.
Effective lithographic techniques are essential to achieving reduction of feature sizes. Lithography impacts the manufacture of microscopic structures not only in terms of directly imaging patterns on the desired substrate, but also in terms of making masks typically used in such imaging. Typical lithographic processes involve formation of a patterned resist layer by patternwise exposing the radiation-sensitive resist to an imaging radiation. The image is subsequently developed by contacting the exposed resist layer with a material (typically an aqueous alkaline developer) to selectively remove portions of the resist layer to reveal the desired pattern. The pattern is subsequently transferred to an underlying material by etching the material in openings of the patterned resist layer. After the transfer is complete, the remaining resist layer is then removed.
For some lithographic imaging processes, the resist used does not provide sufficient resistance to subsequent etching steps to enable effective transfer of the desired pattern to a layer underlying the resist. In many instances (e.g., where an ultrathin resist layer is desired, where the underlying material to be etched is thick, where a substantial etching depth is required, and/or where it is desired to use certain etchants for a given underlying material), a so-called hardmask layer is used intermediate between the resist layer and the underlying material to be patterned by transfer from the patterned resist. The hardmask layer receives the pattern from the patterned resist layer and should be able withstand the etching processes needed to transfer the pattern to the underlying material.
Also, where the underlying material layer is excessively reflective of the imaging radiation used to pattern the resist layer, typically a thin antireflective coating may be applied between the underlying layer and the resist layer. In some instances, the antireflection and hardmask functions may be served by the same material.
While many hardmask and antireflective coating materials exist in the prior art, there is a continued desire for improved compositions. Many of the prior art materials are difficult to apply to the substrate, e.g., they may require use of chemical or physical vapor deposition, and/or high temperature baking. It would be desirable to have antireflective coating/hardmask compositions which could be applied by spin-coating techniques without need for a high temperature bake. Additionally, it is desirable to have hardmask compositions which can be easily etched selective to the overlying photoresist while being resistant to the etch process needed to pattern the underlying layer, especially where the underlying layer is a metal layer.
The invention encompasses novel antireflective coating/hardmask compositions which are useful in lithographic processes. These compositions provide outstanding optical, mechanical and etch selectivity properties while being applicable using spin-on application techniques. The antireflective compositions are characterized by the presence of an SiO containing polymer having pendant chromophore moieties. The invention also encompasses lithographic structures containing the antireflective coating/hardmask composition of the invention, methods of making such lithographic structures and methods of using such lithographic structures to pattern underlying material layers on a substrate.
In one aspect, the invention encompasses a composition suitable for formation of a spin-on antireflective layer, the composition comprising:
(a) a polymer containing SiO moieties and chromophore moieties,
(b) a crosslinking component, and
(c) an acid generator.
The SiO moieties are preferably selected from the group consisting of siloxane moieties and silsesquioxane moieties. The SiO moieties are preferably in a backbone portion of the polymer. The SiO-containing polymer also preferably contains a plurality of reactive sites distributed along the polymer for reaction with the crosslinking component. The acid generator is preferably a thermally activated acid generator.
In another aspect, the invention encompasses a lithographic structure on a substrate, the structure comprising:
(a) an antireflective layer comprising a crosslinked polymer containing SiO moieties and chromophore moieties, and
(b) a radiation-sensitive imaging layer over the antireflective layer.
In another aspect, the invention encompasses method of forming a patterned material feature on a substrate, the method comprising:
(a) providing a material layer on a substrate,
(b) forming an antireflective layer over the material layer, the antireflective layer comprising a crosslinked polymer containing SiO moieties and chromophore moieties,
(c) forming a radiation-sensitive imaging layer over the antireflective layer,
(d) patternwise exposing the imaging layer to radiation thereby creating a pattern of radiation-exposed regions in the imaging layer,
(e) selectively removing portions of the imaging layer and the antireflective layer to expose portions of the material layer, and
(f) etching the exposed portions of the material layer, thereby forming the patterned material feature.
The material to be patterned is preferably a conductive, semiconductive, magnetic or insulative material, more preferably a metal. The SiO moieties are preferably in a backbone portion of the polymer. The SiO-containing polymer also preferably contains a plurality of reactive sites distributed along the polymer for reaction with the crosslinking component.
The invention also encompasses methods of making lithographic structures. These and other aspects of the invention are discussed in further detail below.
The invention encompasses novel antireflective coating/hardmask compositions which are useful in lithographic processes. These antireflective compositions are characterized by the presence of an SiO-containing polymer having pendant chromophore moieties. The invention also encompasses lithographic structures containing the antireflective coating/hardmask composition of the invention, methods of making such lithographic structures and methods of using such lithographic structures to pattern underlying material layers on a substrate.
The antireflective compositions of the invention generally comprise:
(a) a polymer containing SiO moieties and chromophore moieties,
(b) a crosslinking component, and
(c) an acid generator.
The polymer containing SiO moieties may be a polymer containing SiO moieties in the polymer backbone and/or in pendant groups. Preferably, the polymer contains SiO moieties in its backbone. The polymer is preferably an orga-nosiloxane, more preferably organosilsesquioxane. The polymer should have solution and film-forming characteristics conducive to forming a layer by conventional spin-coating. In addition to the chromophore moieties discussed below, the SiO-containing polymer also preferably contains a plurality of reactive sites distributed along the polymer for reaction with the crosslinking component.
Examples of suitable polymers include polymers having the silsesquioxane (ladder or network) structure. Such polymers preferably contain monomers having structures (I) and (II) below:
where R1 comprises a chromophore and R2 comprises a reactive site for reaction with the crosslinking component.
Alternatively, general linear organosiloxane polymers containing monomers (III) and (IV) can be used:
where R1 and R2 are as described above. In some cases, the polymer contain various combinations of monomers (I)-(IV) such that the average structure for R1-containing monomers may be represented as structure (V) below and the average structure for R2-containing monomers may be represented by structure (VI) below:
where x is from about 1 to about 1.5. In theory, x may be greater than 1.5, however, such composition generally do not possess characteristics suitable for spin-coating processes (e.g., they form undesirable gel or precipitate phases).
Generally, silsesquioxane polymers are preferred on the basis of superior etch resistance. If the ordinary organosiloxane polymers are used (e.g., monomers of structures (III) and (IV)), then preferably, the degree of crosslinking is increased compared to formulations based on silsesquioxanes.
The chromophore-containing groups R1 may contain any suitable chromophore which (i) can be grafted onto the SiO-containing polymer (ii) has suitable radiation absorption characteristics, and (iii) does not adversely affect the performance of the layer or any overlying photoresist layers. Preferred chromophore moieties include chrysenes, pyrenes, fluoranthrenes, anthrones, benzophenones, thioxanthones, and anthracenes. Anthracene derivatives, such as those described in U.S. Pat. No. 4,371,605 may also be used; the disclosure of this patent is incorporated herein by reference. 9-anthracene methanol is a preferred chromophore. The chromophore moiety preferably does not contain nitrogen, except for possibly deactivated amino nitrogen such as in phenol thiazine.
The chromophore moieties may be chemically attached to the SiO containing polymer by acid-catalyzed O-alkylation or C-alkylation such as by Friedel-Crafts alkylation. Alternatively, the chromophore moiety may be attached by an esterification mechanism. A preferred acid for Friedel-Crafts catalysis is HCl. Preferably, about 15 to 40% of the functional groups (R1) contain chromophore moieties. In some instances, it may be possible to bond the chromophore to the monomer before formation of the SiO-containing polymer, however this is generally not preferred. The site for attachment of the chromophore is preferably an aromatic group such as a hydroxybenzyl or hydroxymethylbenzyl group. Alternatively, the chromophore may be attached by reaction with other moieties such as cyclohexanol or other alcohols. The reaction to attach the chromophore is preferably an esterification of the alcoholic OH group.
R2 comprises a reactive site for reaction with the crosslinking component. Preferred reactive moieties contained in R2 are alcohols, more preferably aromatic alcohols (e.g., hydroxybenzyl, phenol, hydroxymethylbenzyl, etc.) or cycloaliphatic alcohols (e.g., cyclohexanoyl). Alternatively, non-cyclic alcohols such as fluorocarbon alcohols, aliphatic alcohols, amino groups, vinyl ethers, and epoxides may be used.
Preferably, the SiO-containing polymer (before attachment of the chromophore) is poly(4-hydroxybenzylsilsesquioxane). Examples of other silsesquioxane polymers of the invention include:
poly(p-hydroxyphenylethylsilsesquioxane),
poly(p-hydroxyphenylethylsilsesquioxane-co-p-hydroxy-xcex1-methylbenzylsilsesquioxane),
poly(p-hydroxyphenylethylsilsesquioxane-co-methoxybenzylsilsesquioxane),
poly(p-hydroxyphenylethylsilsesquioxane-co-t-butylsilsesquioxane),
poly(p-hydroxyphenylethylsilsesquioxane-co-cyclohexylsilsesquioxane),
poly(p-hydroxyphenylethylsilsesquioxane-co-phenylsilsesquioxane),
poly(p-hydroxyphenylethylsilsesquioxane-co-bicycloheptylsilsesquioxane),
poly(p-hydroxy-xcex1-methylbenzylsilsesquioxane),
poly(p-hydroxy-xcex1-methylbenzylsilsesquioxane-co-p-hydroxybenzylsilsesquioxane),
poly(p-hydroxy-xcex1-methylbenzylsilsesquioxane-co-methoxybenzylsilsesquioxane),
poly(p-hydroxy-xcex1-methylbenzylsilsesquioxane-co-t-butylsilsesquioxane),
poly(p-hydroxy-xcex1-methylbenzylsilsesquioxane-co-cyclohexylsilsesquioxane),
poly(p-hydroxy-xcex1-methylbenzylsilsesquioxane-co-phenylsilsesquioxane),
poly(p-hydroxy-xcex1-methylbenzylsilsesquioxane-co-bicycloheptylsilsesquioxane), and
poly(p-hydroxybenzylsilsesquioxane-co-p-hydroxyphenylethylsilsesquioxane). The polyorganosiloxane polymers described in U.S. Pat. No. 5,100,503 are generally not useful for creating low temperature bake compositions due to their very low reactivity with crosslinking components; the disclosure of this patent is incorporated herein by reference.
The SiO-containing polymers of the invention preferably have a weight average molecular weight, before reaction with the crosslinking component, of at least about 1000, more preferably a weight average molecular weight of about 1000-10000.
The crosslinking component is preferably a crosslinker that can be reacted with the SiO containing polymer in a manner which is catalyzed by generated acid and/or by heating. Generally, the crosslinking component used in the antireflective compositions of the invention may be any suitable crosslinking agent known in the negative photoresist art which is otherwise compatible with the other selected components of the composition. The crosslinking agents preferably act to crosslink the polymer component in the presence of a generated acid. Preferred crosslinking agents are glycoluril compounds such as tetramethoxymethyl glycoluril, methylpropyltetramethoxymethyl glycoluril, and methylphenyltetramethoxymethyl glycoluril, available under the POWDERLINK trademark from American Cyanamid Company. Other possible crosslinking agents include: 2,6-bis(hydroxymethyl)-p-cresol, compounds having the following structures:
including their analogs and derivatives, such as those found in Japanese Laid-Open Patent Application (Kokai) No. 1-293339, as well as etherified amino resins, for example methylated or butylated melamine resins (N-methoxymethyl- or N-butoxymethyl-melamine respectively) or methylated/butylated glycolurils, for example as can be found in Canadian Patent No. 1 204 547. Other crosslinking agents such as bis-epoxies or bis-phenols (e.g., bisphenol-A) may also be used. Combinations of crosslinking agents may be used.
The acid generator is preferably an acid generator compound is employed that liberates acid upon thermal treatment. A variety of known thermal acid generators are suitably employed such as e.g. 2,4,4,6-tetrabromocyclohexadienone, benzoin tosylate, 2-nitrobenzyl tosylate and other alkyl esters of organic sulfonic acids. Compounds that generate a sulfonic acid upon activation are generally suitable. Other suitable thermally activated acid generators are described in U.S. Pat. Nos. 5,886,102 and 5,939,236; the disclosures of these two patents are incorporated herein by reference. If desired, a radiation-sensitive acid generator may be employed as an alternative to a thermally activated acid generator or in combination with a thermally activated acid generator. Examples of suitable radiation-sensitive acid generators are described in U.S. Pat. Nos. 5,886,102 and 5,939,236. Other radiation-sensitive acid generators known in the resist art may also be used as long as they are compatible with the other components of the antireflective composition. Where a radiation-sensitive acid generator is used, the cure (crosslinking) temperature of the composition may be reduced by application of appropriate radiation to induce acid generation which in turn catalyzes the crosslinking reaction. Even if a radiation-sensitive acid generator is used, it is preferred to thermally treat the composition to accelerate the crosslinking process (e.g., for wafers in a production line).
The antireflective compositions of the invention preferably contain (on a solids basis) (i) about 50-98 wt. % of the SiO-containing polymer, more preferably about 70-80 wt. %, (ii) about 1-50 wt. % of crosslinking component, more preferably about 3-25%, most preferably about 5-25 wt. %, and (iii) about 1-20 wt. % acid generator, more preferably about 1-15 wt. %.
The antireflective coating/hardmask compositions of the Invention may be used in combination with any desired resist material in the forming of a lithographic structure. Preferably, the resist is imageable with ultraviolet radiation (e.g. less than 400 nm wavelength) or with electron beam radiation. Examples of suitable resist materials are described in U.S. Pat. Nos. 5,861,231; 5,962,184; and 6,037,097, the disclosures of which are incorporated herein by reference.
The antireflective compositions of the invention will typically contain a solvent prior to their application to the desired substrate. The solvent may be any solvent conventionally used with resists which otherwise does not have any excessively adverse impact on the performance of the antireflective composition. Preferred solvents are propylene glycol monomethyl ether acetate, cyclohexanone, and ethyl cellosolve acetate. The amount of solvent in the composition for application to a substrate is preferably sufficient to achieve a solids content of about 8-20 wt. %. Higher solids content formulations will generally yield thicker coating layers. The compositions of the invention may further contain minor amounts of auxiliary components (e.g., base additives, etc.) as may be known in the art.
The antireflective compositions of the invention can be prepared by combining the polymer, crosslinking component and acid generator, and any other desired ingredients using conventional methods. The compositions of the invention advantageously may be formed into antireflective layers on a substrate by spin-coating followed by baking to achieve crosslinking and solvent removal. The baking is preferably conducted at about 250xc2x0 C. or less, more preferably about 150xc2x0-200xc2x0 C., most preferably about 170xc2x0-180xc2x0 C. The baking time may be varied depending on the layer thickness and bake temperature. A typical time at 170xc2x0 would be about two minutes. The thickness of the antireflective composition of the invention may be varied depending on the desired function. For example, where the composition is used as a non-planarizing antireflective coating, the thickness may be about 50-500 nm. Where the composition is used as a planarizing hardmask, the thickness is preferably about 0.5-5.0 xcexcm. If desired, the compositions of the invention may also be used as dielectric materials in a similar manner to conventional spin-on glass materials.
The compositions of the invention are especially useful for lithographic processes used in the manufacture of integrated circuits on semiconductor substrates. The compositions are especially useful for lithographic processes using mid-UV, 248 nm deep UV, x-ray, or e-beam or other imaging radiation.
Semiconductor lithographic applications generally involve transfer of a pattern to a layer of material on the semiconductor substrate. The material layer of the semiconductor substrate may be a metal conductor layer, a ceramic insulator layer, a semiconductor layer or other material depending on the stage of the manufacture process and the desired material set for the end product. The composition of the invention is preferably applied directly over the material layer to be patterned, preferably by spin-coating. The composition is then baked to remove solvent and cure (crosslink) the composition. A radiation-sensitive resist layer can then be applied (directly or indirectly) over the cured antireflective composition of the invention.
Typically, the solvent-containing resist composition is applied using spin coating or other technique. The substrate with the resist coating is then preferably heated (pre-exposure baked) to remove the solvent and improve the coherence of the resist layer. The thickness of the applied layer is preferably as thin as possible with the provisos that the thickness is preferably substantially uniform and that the resist layer be sufficient to withstand subsequent processing (typically reactive ion etching) to transfer the lithographic pattern to the underlying substrate material layer. The pre-exposure bake step is preferably conducted for about 10 seconds to 15 minutes, more preferably about 15 seconds to one minute. The pre-exposure bake temperature may vary depending on the glass transition temperature of the photoresist.
After solvent removal, the resist layer is then patternwise-exposed to the desired radiation (e.g. 248 nm ultraviolet radiation). Where scanning particle beams such as electron beam are used, patternwise exposure may be achieved by scanning the beam across the substrate and selectively applying the beam in the desired pattern. More typically, where wavelike radiation forms such as 248 nm ultraviolet radiation, the patternwise exposure is conducted through a mask which is placed over the resist layer. For 248 nm UV radiation, the total exposure energy is preferably about 100 millijoules/cm2or less, more preferably about 50 millijoules/cm2or less (e.g. 15-30 millijoules/cm2).
After the desired patternwise exposure, the resist layer is typically baked to further complete the acid-catalyzed reaction and to enhance the contrast of the exposed pattern. The post-exposure bake is preferably conducted at about 60-175xc2x0 C., more preferably about 90-160xc2x0 C. The post-exposure bake is preferably conducted for about 30 seconds to 5 minutes.
After post-exposure bake, the resist structure with the desired pattern is obtained (developed) by contacting the resist layer with an alkaline solution which selectively dissolves the areas of the resist which were exposed to radiation. Preferred alkaline solutions (developers) are aqueous solutions of tetramethyl ammonium hydroxide. The resulting lithographic structure on the substrate is then typically dried to remove any remaining developer solvent.
The pattern from the resist structure may then be transferred to the exposed portions of the layer of antireflective material of the invention by etching with CF4 or other suitable etchant using techniques known in the art.
After the opening of the layer of antireflective material of the invention and any underlying antireflective coating, the underlying material layer to be patterned may then be etched using an etchant appropriate to the material layer composition. Where the material layer is a metal (e.g., Cr) a combination of Cl2/O2 may be used as a dry etchant. Once the desired pattern transfer has taken place, any remaining resist may be removed using conventional stripping techniques. If the composition of the invention is being used strictly as a hardmask or non-planarizing antireflective coating, the composition of the invention may be removed by contacting with a CF4/O2 plasma.
Thus, the compositions of the invention and resulting lithographic structures can be used to create patterned material layer structures such as metal wiring lines, holes for contacts or vias, insulation sections (e.g., damascene trenches or shallow trench isolation), trenches for capacitor structures, etc. as might be used in the design of integrated circuit devices. The compositions are especially useful in the context of creating patterned metal structures, especially Cr-based structures useful as masks.

Antireflective silicon-containing compositions as hardmask layer

International Business Machines Corporation


A multilayer polymeric film comprises:

The present invention relates to a multilayer polymeric film. More particularly, the present invention relates to an improved multilayer polymeric film in which the coefficient of friction (COF) and the release character of the film are less susceptible to, or more resistant to, handling or mishandling during further treatment of the film by various users (e.g., converters). Additionally, the present invention relates to cold seal release films comprising such improved multilayer polymeric films.
Multilayer polymeric films are used to manufacture cold seal release films that may be reverse-printed and laminated to a variety of substrates. In certain applications, it may be desirable to treat (e.g., by corona or flame treatment) a surface (e.g., the print face) of the multilayer polymeric film. During the treatment, however, the opposite surface (i.e., the release face) may be treated in addition to, or instead of, the intended surface through so-called xe2x80x9cbackside treatmentxe2x80x9d or through operator error. Such handling or mishandling may detrimentally affect the COF and release character of the film.
Thus, it would be desirable to provide a multilayer polymeric film that is less susceptible to, or more resilient to, the above-described xe2x80x9cbackside treatmentxe2x80x9d or mishandling by the operator. That is, it would be desirable to provide a multilayer layer polymeric film that possesses a stable COF and good release character in spite of such treatment or mishandling.
The present invention provides an effective solution to the above-described problem.
U.S. Pat. No. 4,692,379 to Keung, et al. discloses a film having an upper heat sealable layer formed from an ethylene-propylene-containing copolymer or terpolymer and an antiblocking agent and a lower heat sealable layer formed from an ethylene-propylene-containing copolymer or terpolymer and antiblocking agent and a quantity of silicone oil such that the coefficient of friction-reducing amount of the silicone oil will be present on an exposed surface of the upper heat sealable layer following mutual contact of the upper and lower surfaces. The silicone oil additive is described as having a viscosity of from about 350 to about 100,000 centistokes, with about 10,000 to about 30,000 centistokes being preferred. An advantage of the invention as described in the ""379 patent is that the silicone is present on the exposed surface of the lower layer in discrete microglobules which, to some extent, transfer to the upper surface upon contact. The silicone on the surfaces of the film facilitates machinability.
U.S. Pat. No. 4,734,317 to Bothe, et al. discloses a biaxially oriented multilayer polyolefin film which comprises a polypropylene base layer, a first polyolefin sealing layer positioned on one side of the base layer, and containing from about 0.5% to 3% by weight of incorporated polydialkylsiloxane, the first sealing layer not being subject to corona treatment, and a second polyolefin sealing layer positioned on the other side of the base layer and having a coating of the polydialkylsiloxane on its outer surface, the second sealing layer being subject to corona treatment, wherein the polydialkylsiloxane coating is formed by contact of the first and second layers.
U.S. Pat. No. 4,925,728 to Crass, et al. discloses a biaxially stretched multilayer film comprising a base layer essentially comprising polypropylene and at least one top layer, wherein the top layer essentially comprises (a) 98.5% to 99.6% by weight of a propylene homopolymer and (b) 0.4% to 1.5% by weight of a polydiorganosiloxane, relative to the top layer.
U.S. Pat. No. 5,482,780 to Wilkie, et al. discloses a polypropylene film with cold seal release and cold seal receptive surfaces, wherein a predominantly isotactic polypropylene homopolymer core has on one side thereof an ethylene-propylene random copolymer having a physically modified surface for reception of a cold seal cohesive composition and on the other side of the core there is a blend of an ethylene-butylene copolymer and an ethylene-propylene random copolymer containing a non-migratory slip agent. The preferred non-migratory slip agent is described as being a crosslinked silicone having a particle size of about 1 to 4.5 microns, such as that identified by TOSPEARL of Toshiba Company.
U.S. Pat. No. 5,489,473 to Wilkie discloses biaxially oriented polypropylene cold seal packaging films comprising at least one cold seal release layer and a cold seal receptive layer. The use of crosslinked silicone in the cold seal release skin layer is also disclosed.
U.S. Pat. No. 5,792,549 to Wilkie discloses a coextruded biaxially oriented polyolefin packaging film comprising a cold seal release layer, a core layer, and a cold seal receptive skin layer. The use of crosslinked silicone having a particle size of about 1 to about 4.5 microns such as that identified by TOSPEARL of Toshiba Company is also disclosed.
U.S. Pat. No. 5,798,174 to Wilkie discloses cold sealable films for heat sensitive packaging operations comprising, in order, a cold seal cohesive layer, a core layer, and a cold seal release layer comprising a mixture of about 1 to about 80% by weight butene-propylene copolymer and about 99 to 20% by weight butylene-ethylene copolymer.
U.S. Pat. No. 5,840,419 to Alder discloses a multilayer polyolefin film comprising a core layer of a propylene polymer and an outer polyolefin layer on the core layer, the outer polyolefin layer including a coefficient reducing amount of a particulate, partially crosslinked polysiloxane, which are preferably in the form of elastomeric particles including polysiloxane in the form of silicone oil. The patent states that the silicone oil is released when the particles are xe2x80x9csubjected to mechanical stress.xe2x80x9d
The present invention is directed to a multilayer polymeric film comprising:
(a) a core layer comprising a thermoplastic polymer and optionally an antistatic agent, the core layer having a first side and a second side;
(b) a functional layer which is printable or sealable or treatable for printing or sealing on the first side of the core layer; and
(c) an additional layer on the second side of the core layer comprising a polypropylene homopolymer, a solid antiblock, and silicone oil.
In another embodiment, the present invention relates to a cold seal release film comprising:
(a) a core layer comprising a thermoplastic polymer and optionally an antistatic agent, the core layer having a first side and a second side;
(b) a functional layer which is printable or sealable or treatable for printing or sealing on the first side of the core layer; and
(c) an additional layer on the second side of the core layer comprising a polypropylene homopolymer, a solid antiblock, and silicone oil.
In yet another embodiment, the present invention provides a process for producing a multilayer polymeric film comprising:
(a) coextruding a core layer comprising a thermoplastic polymer and optionally an antistatic agent, a functional layer which is printable or sealable or treatable for printing or sealing, and an additional layer comprising a polypropylene homopolymer, a solid antiblock, and silicone oil;
(b) cooling the coextruded film; and
(c) optionally orienting the film in at least the machine and/or transverse directions.
It has been found that the present invention provides a multilayer polymeric film which exhibits a stable COF and good release character, even when the film is subjected to treatment or mishandling known to detrimentally affect COF and release character.
The core layer comprises a thermoplastic polymer which has properties suitable for extrusion or coextrusion followed by biaxial orientation in the machine and transverse directions under elevated temperature so as to form a multi-layer film. Although the preferred thermoplastic polymer of the core layer is a polypropylene homopolymer, other polymers may be used. These polymers include any polymer made from a 2 to 4 carbon atom olefin, such as ethylene or butene-1, or a polymer made predominantly of propylene with minor amounts of another olefin, usually a 2 to 4 carbon atom olefin.
Optionally, the core layer comprises an antistatic agent in addition to the thermoplastic polymer. The antistatic agent may be selected from, e.g., glycerol monostearate (GMS) and a blend of GMS and tertiary amine. Suitable amounts for the antistatic agent may range from about 0.05% to about 3 weight %, based upon on the weight of the core layer.
The functional layer may comprise a polymer having properties suitable for extrusion and uniaxial or biaxial orientation (by stretching the extrudate in the machine and/or transverse directions under elevated temperatures) and for forming skin layers on the outer surfaces of the core layer. Suitable polymers include an olefinic polymer, such as polypropylene or polyethylene. Other suitable polymers include a copolymer or terpolymer of ethylene, propylene and/or butylene and/or another olefin having 5 to 10 carbon atoms or a mixture of these olefin polymers. Preferably, the functional layer comprises an ethylene homopolymer having a density of about 0.91 to about 0.96 g/cm3, an ethylene-propylene copolymer in which the ethylene content is about 2 to about 10% by weight based upon the total weight of the copolymer, or an ethylene-propylene-butylene terpolymer in which the ethylene content is about 0.5 to about 7 weight % ethylene and about 5 to about 30 weight % butylene, each based upon the total weight of the terpolymer.
The additional layer of the present invention is comprised of a polypropylene homopolymer.
It has been discovered that it may be particularly advantageous to use a highly crystalline polypropylene (HCPP) as the polypropylene homopolymer contained in the additional layer. We have found that the use of HCPP provides additional benefits, including an overall improvement in the release properties of the film. HCPP polypropylene polymers include those having a decalin solubles content of about 1 to about 5% by weight, meso pentads equal to or greater than about 85% (13C NMR spectroscopy), and a melt flow of about 2.5 to about 3 (as measured according to the standard ASTM D1238 test for polypropylene).
Suitable commercially available HCPP polymers include, but are not limited to, Amoco 9218 HCPP resin from BP-Amoco.
The additional layer of the present invention also contains a solid antiblock. The solid antiblocks of the present invention are such that they do not substantially break up when subjected to mechanical stress like the particulate, partially cross-linked polysiloxanes described in U.S. Pat. No. 5,840,419. Suitable antiblocks include, but are not limited to, fully crosslinked or non-meltable polysiloxane, polymethyl methacrylate (PMMA) particles such as EPOSTAR(copyright) MA-1002 or silica particles such as SYLOBLOC 44 from W. R. Grace.
In a preferred embodiment, the solid antiblock is present in the form of spherical particulates. Preferably, the solid antiblock is a fully crosslinked or non-meltable polysiloxane, which in combination with the silicone oil, provides a multilayer film having the desired properties according to the present invention. In a most preferred embodiment, the fully crosslinked or non-meltable polysiloxane is polymethylsilsesquioxane, which comes in a spherical powder form having an average particle size of from about 2 xcexcm to about 6 xcexcm. These materials are completely solid with no known melting point.
Suitable fully crosslinked or non-meltable polysiloxanes include, but are not limited to, TOSPEARL T120A, which is a fully crosslinked, non-meltable silicone resin powder available from Toshiba Silicone Company, Ltd.
The solid antiblock may be incorporated into the additional layer in an amount ranging from about 0.1 to about 0.5% by weight, preferably from about 0.15 to about 0.30% by weight, based on the entire weight of the additional layer.
The additional layer of the present invention also contains silicone oil, e.g. polydimethylsiloxane. The silicone oil used may range from about 1,000 centistoke (cs) viscosity to about 100,000 cs viscosity. The preferred silicone oils are those having a viscosity of about 30,000 to about 60,000 cs, such as 20/30,0000 polydimethylsiloxane fluid from Dow-Corning or 200/60,0000 polydimethylsiloxane fluid from Dow-Corning.
The silicone oil may be incorporated into the additional layer in an amount ranging from about 0.1 to about 2% by weight, preferably from about 0.2 to about 0.8% by weight, based on the entire weight of the additional layer.
The functional layer includes those thermoplastic polymer skin layers suitable for being treated for printing or sealing or by being a thermoplastic polymer which is printable or sealable without treatment. As mentioned previously, the functional layer may be selected from the group consisting of ethylene or propylene homopolymer, ethylene-propylene copolymer or ethylene-propylene-butylene terpolymer or a mixture of two or more of such homopolymer, copolymer or terpolymer. In one embodiment of the invention, the surface of the functional layer is treated by surface treatment which improves wettability and adhesion of printed matter (print may be by lithography, liquid or dry toner, thermal dyes, dye sublimation, etc.). In another embodiment of the invention, the functional layer is a cold seal adhesion promoting layer.
It is contemplated that the additional layer will provide excellent antiblocking properties to any commercially applied cold seal receptive composition or print receptive surface.
The functional layer may itself be printable or sealable or may be treated so as to provide sealability and/or printability. This includes surface treatment of any kind known to enhance the surface tension properties such as flame or corona treatment. Other treatment methods include the application of a printable or sealable covering layer by way of any conventional extrusion or coating method. Certain water-based coatings are known for their utility as cold-sealable coatings or printable coatings. Examples include acrylic-based coatings including alkyl acrylate polymers and copolymers.
Sometimes it is useful to enhance or provide the film with certain properties by use of appropriate film additives. Such additives are used in effective amounts, which vary depending upon the property required, and are, typically selected from the group consisting of: antistatic, antiblock, slip, antioxidant, moisture or gas barrier additive. These additives may be added to one or more layers of the film according to the present invention.
Useful antistatic additives which can be used in amounts ranging from about 0.05 to about 3 weight %, based upon the weight of the layer, include alkali metal sulfonates, polyether-modified polydiorganosiloxanes, polyalkylphenylsiloxanes and tertiary amines. As discussed previously for the core layer, the antistatic agent may be GMS or a blend of GMS and tertiary amine.
Useful antiblock additives used in amounts ranging from about 0.1 weight % to about 3 weight % based upon the entire weight of the layer include inorganic particulates such as silicon dioxide, e.g. a particulate antiblock sold by W.R. Grace under the trademark SYLOBLOC 44, Sipernat from Degussa, calcium carbonate, magnesium silicate, aluminum silicate, calcium phosphate, and the like (e.g. KAOPOLITE). Another useful particulate antiblock agent is TOSPEARL made by Toshiba Silicone Co., Ltd. and is described in U.S. Pat. No. 4,769,418. Another useful antiblock additive is a spherical particle made from methyl methacrylate resin having an average diameter of 1 to 15 microns, and such an additive is sold under the trademark EPOSTAR and is commercially available from Nippon Shokubai. Experimental results show that with addition of particulate antiblock additives such as EPOSTAR MA1002-1010, TOSPEARL 145, KAOPOLITE 1152, SYLOBLOC 44 do not materially effect release property of the film but do reduce the coefficient of friction properties of the film.
Typical slip additives include higher aliphatic acid amides, higher aliphatic acid esters, waxes and metal soaps, which can be used in amounts ranging from about 0.1 to about 2 weight percent based on the total weight of the layer. A specific example of a useful fatty amide slip additive is erucamide. Useful antioxidants are, generally used in amounts ranging from about 0.1 weight % to about 2 weight percent, based on the total weight of the layer, phenolic antioxidants. One useful antioxidant is commercially available under the trademark IRGANOX 1010.
Barrier additives are used in useful amounts and may include low-molecular weight resins, hydrocarbon resins, particularly petroleum resins, styrene resins, cyclopentadiene resins and terpene resins.
Optionally, the outer layers are compounded with a wax for lubricity. Amounts of wax range from about 2 to about 15 weight % based on the total weight of the layer.
In the present invention, the cold seal release film may also comprise additional coatings and/or layers such as an adhesive layer (e.g., a water-based urethane coating), a metallized polyester layer, and/or a cold seal layer (e.g., Technical Coatings 30061A, which is a pattern applied coating comprising polyisoprene and ethylene-vinyl acetate copolymer), as is well known in the art.
Typically, the film is formed by coextruding the thermoplastic polymer-containing core layer together with the additional and functional layers through a flat sheet extruder die at a temperature ranging from between about 200 to about 275xc2x0 C., casting the film onto a cooling drum and quenching the film. The sheet is then stretched about 4 to about 6 times in the machine direction (MD) orienter followed by stretching about 6 to about 10 times in the transverse direction (TD) orienter. The film is then wound onto a reel. Optionally, one of the external surfaces is coated or flame or corona treated before winding (i.e., the surface of the functional layer). In addition, the production process may also be modified to include an adhesive layer on one or both surfaces of the multilayer polymeric film, a metallized polyester layer, and a cold seal layer.
In general, the film of the instant invention comprises at least three layers: the core layer, the additional layer (usually the outermost skin layer), and the layer which is functional (also usually the outermost skin later). However, it is contemplated that intermediate layers can be incorporated between the core layer and the outermost skin layers. The core layer usually represents about 70 to about 90 percent of the thickness of the total multilayer polymeric film. The skin layers are usually coextensively applied to each major surface of the core layer, typically by coextrusion, as noted above. As indicated previously, however, the additional layer or the functional layer may not, ultimately, be the outermost layers.

Abstract: A multilayer polymeric film comprises:

Abstract: (c) an additional layer on the second side of the core layer comprising a polypropylene homopolymer, a solid antiblock, and silicone oil. The film has a stable coefficient of friction and release character in spite of mishandling during treatment.